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Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

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Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

#61

Post by tptacek »

chc4 wrote: post #15

LLL lattice reduction is the same algorithm that can be used for cracking PuTTY keys from biased nonces from the CVE a few days ago. 'tptacek explained a bit about the attack (and links to a cryptopals problem for it, which I can almost pretend to understand if I squint) https://news.ycombinator.com/item?id=40045377 In a similar vein, the SciCraft minecraft server had a creeper farm which used some sort of black magi…

Sean and Kelby do a much better job of describing what LLL is, but this is maybe the best explanation of why LLL is that I've ever read. In all three cases, you only need basic linear algebra, if that (Kelby wants you to grok Gram-Schmidt, which is like just before the midterm of an undergrad linear algebra 101).

I really don't have words for how great this post is. It made my week.

Later

A really concise explanation of the same process you can step through in Python:

https://crypto.stackexchange.com/questions/37836/problem-wit...

Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

#62

Post by shthed »

timdierks wrote: post #23
dzdt wrote: post #9

Back in 1999-2000 there was an "International RoShamBo Programming Competition" [1] where computer bots competed in the game of rock-paper-scissors. The baseline bot participant just selected its play randomly, which is a theoretically unbeatable strategy. One joke entry to the competition was carefully designed to beat the random baseline ... by reversing the state of the random number generator and then predicting…

That's me! Thanks for pulling up the quote from long ago: > "With his obvious technical skill, and his "cheat early and often" attitude, Tim could have a promising career as an AI programmer in the computer games industry. :)" Instead took a path of security, authoring the TLS RFC and principal engineer in Google security. Thanks for the flashback.

Can you share the source to Nostradamus?

Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

#63

Post by tptacek »

leijurv wrote: post #56
danielwmayer wrote: post #44

Yo Leijurv this is so sick! As a fellow game hacker this sort of stuff is super inspiring. My girlfriend and I watch all the fitmc videos even though neither of us play minecraft, and love the ones detailing your insane tooling the most. Ever since we watched the nocom one I’ve wondered what you do professionally - are you in the infosec space? With the amount of math and computer science knowledge you put into your…

I'm just a regular SWE! Infosec or algorithmic trading - maybe someday.

This is you? You're fully qualified.

Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

#64

Post by lyu07282 »

chc4 wrote: post #15

LLL lattice reduction is the same algorithm that can be used for cracking PuTTY keys from biased nonces from the CVE a few days ago. 'tptacek explained a bit about the attack (and links to a cryptopals problem for it, which I can almost pretend to understand if I squint) https://news.ycombinator.com/item?id=40045377 In a similar vein, the SciCraft minecraft server had a creeper farm which used some sort of black magi…

There is also some Rng manipulation to make blocks always drop the maximum, explained here:

https://youtu.be/ZcdN1wCJPqM?t=390

Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

#65

Post by alickz »

eru wrote: post #60
dzdt wrote: post #9

Back in 1999-2000 there was an "International RoShamBo Programming Competition" [1] where computer bots competed in the game of rock-paper-scissors. The baseline bot participant just selected its play randomly, which is a theoretically unbeatable strategy. One joke entry to the competition was carefully designed to beat the random baseline ... by reversing the state of the random number generator and then predicting…

I remember someone doing the same to an online poker site that had helpfully documented its PRNG in a laudable attempt at transparency. (And the transparency got them an improvement in their security in the end.)

I'm surprised they don't use some form of hardware based RNG. I assume there's many good reasons

https://en.wikipedia.org/wiki/Hardware_random_number_generat...

Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

#67

Post by eru »

alickz wrote: post #65
eru wrote: post #60

Earlier quoted context omitted.

I remember someone doing the same to an online poker site that had helpfully documented its PRNG in a laudable attempt at transparency. (And the transparency got them an improvement in their security in the end.)

I'm surprised they don't use some form of hardware based RNG. I assume there's many good reasons https://en.wikipedia.org/wiki/Hardware_random_number_generat...

They wanted to show that they didn't cheat.

In general, you can pick a random seed at the start of the day, commit to it somewhere (eg publish a hash of it on the bitcoin blockchain, or just on your website), then use that seed in a cryptographically secure PRNG on your website all day, and at the end of the day you publish the seed you already committed to.

This way people can check that you didn't cheat, but can't guess their opponents cards either.

Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

#68

Post by bagels »

dzdt wrote: post #9

Back in 1999-2000 there was an "International RoShamBo Programming Competition" [1] where computer bots competed in the game of rock-paper-scissors. The baseline bot participant just selected its play randomly, which is a theoretically unbeatable strategy. One joke entry to the competition was carefully designed to beat the random baseline ... by reversing the state of the random number generator and then predicting…

So, it was using a pseudorandom generator?

Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

#69

Post by logtempo »

alickz wrote: post #65
eru wrote: post #60

Earlier quoted context omitted.

I remember someone doing the same to an online poker site that had helpfully documented its PRNG in a laudable attempt at transparency. (And the transparency got them an improvement in their security in the end.)

I'm surprised they don't use some form of hardware based RNG. I assume there's many good reasons https://en.wikipedia.org/wiki/Hardware_random_number_generat...

https://www.random.org/
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